Devices that integrate the functions of both display and image capture have been proposed for use in videoconferencing and other functions, as described in commonly assigned U.S. Pat. No. 7,714,923 entitled “Integrated display and capture apparatus” to Cok et al. In such devices, the camera components used for image capture are integrally formed to share space with display components on the surface of the same screen. This advantageous arrangement helps to allow a more natural interaction between viewers positioned at their respective displays. The term “displays that see (DTS)” has been coined to describe a class of such devices.
Increased demand for more compact device packaging presents a particular challenge for DTS designs. To provide a handheld device of this type, such as a camera with a display visible to the subject, it is necessary to reduce device dimensions and weight as much as possible, without compromising its display or image capture functions.
With conventional optical solutions for camera optics, there are trade-offs between size and thickness of the DTS device and image quality. The optical path length can be severely constrained, increasing optical design complexity and cost. Placing one or more cameras behind the display screen can add significant thickness and bulk and may be impractical for a hand-held device. Positioning one or more cameras along edges of the display screen may alleviate some of the dimensional problems, but proves to be less satisfactory because the perspective of the camera is different from the perspective of a viewer who is observing the display.
In transparent displays, cameras in the display area obstruct the transparency of the display. While displays such as active matrix OLEDs (AMOLED) can be highly transparent, camera components such as an image sensor are typically opaque. What is needed is a method to capture an image from the perspective of the center of the display while locating the opaque components of the camera at the edge of the display. In the paper “Liquid Crystal Based Optical Switches” by Semenova et al (Journal of Molecular Crystals and Liquid Crystals, Vol. 413, pp. 385-398, 2004), optical switches are provided that redirect light when activated. However, the optical switches described are dependent on the light being polarized and prisms are used to increase the angular redirection of the optical switch. As such, the optical switches described are not suited for use in a transparent display because the light interacting with the display is not polarized and prisms would distort the transparent view through the transparent display.
U.S. Pat. No. 4,385,799 to Soref, entitled “Dual array fiber liquid crystal optical switches,” presents an optical switch for telecommunications that is based on liquid crystals. In this case, a reflection from a liquid crystal layer is used to interrupt a beam of light. As such, a small deflection of the beam of light is sufficient to interrupt the beam and switch OFF the telecommunication. The deflection provided by this optical switch, however, is slight, and is too small to be used in a transparent display.
U.S. Pat. No. 5,018,835 to Dorschner, entitled “Deflector for an optical beam including refractive means,” provides a deflector for an optical beam based on a liquid crystal layer. In this patent, a prism element is combined with a series of stripe electrodes to deflect an optical beam by different amounts. U.S. Pat. No. 6,999,649 to Chen, entitled “Optical switches made by nematic liquid crystal switchable mirrors, and apparatus of manufacture,” provides a similar deflector which includes a prism element to increase the angle of deflection. Since these deflectors utilize prism elements, they would provide distorted views through transparent displays.
U.S. Pat. No. 6,687,030 to Popovich et al., entitled “Method and apparatus for illuminating a display,” discloses an image generating apparatus including a switchable light-directing apparatus. In response to a control signal, the switchable light-directing apparatus directs portions of received light onto different regions of an image plane.
U.S. Pat. No. 6,885,414 to Li, entitled “Optical router switch array and method for manufacture,” discloses an optical router switch array including a plurality of individually switchable mirror elements. The switchable mirror elements are made using liquid crystal holographic gratings.
Although various configurations have been proposed for providing a DTS design, conventional solutions fall short of a solution that reduces the physical profile of the device, provides alignment between the perspective of the camera and the perspective of the display as observed by a viewer, and conceals or masks image capture components from visibility to the viewer who is also being imaged. Thus, it is seen that there is a need for an improved DTS design that addresses these difficulties.